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Railways RRB (Assistant Loco Pilot & Technician) Solved Paper-2 (2014)

  • question_answer
    A simple microscope consists of a concave lens of power \[-\text{ }10\text{ }D\]and a convex lens of power \[+\text{ }20\text{ }D\]in contact. If the image formed at infinity, then calculate the magnifying power (D = 25 cm)

    A)  \[2.5\]                         

    B)  \[3.5\]

    C)  \[2.0\]                         

    D)  \[3.0\]

    Correct Answer: A

    Solution :

    Power of combination, \[P={{P}_{1}}+{{P}_{2}}\] \[P=+20-10=+10D\] \[F=\frac{1}{P}=\frac{1}{10}m=\frac{100}{10}cm=10cm\] For final image at infinity \[M=\frac{D}{F}=\frac{25}{10}=2.5\]


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